The present invention relates in general to biosensors and, more particularly, to biosensors for use in monitoring climate control processes, such as heating, ventilating, air conditioning and refrigeration processes.
Biosensors are chemical sensors comprising three basic elements: a reactive biocomponent element, a base sensor element and an interface element disposed therebetween. The biocomponent includes a bioagent, such as bioactive species or biomimetic species, selected to interact specifically with a particular analyte to be sensed. The bioagent, typically through a biochemical process, acts to bind or convert the analyte into a measurable component. Biocomponents used in conventional sensors include biological species such as enzymes, antigens, antibodies, receptors, tissues, whole cells, cell organelles, bacteria and nucleic acids. The sensor element comprises a physical component operative to generate a measurable output, usually an electrical or optical signal, indicative of the presence of the analyte and, in certain instances, the actual amount of the analyte. Sensor elements used in conventional sensors include, for example, electrochemical devices, optical devices, acoustical devices and calorimetric devices. The interface element comprises a membrane or coating that separates the sensor from the biocomponent and serves as a link between the two. Examples of interfaces used in conventional biosensors include polymer membranes, electropolymerized coatings and self-assembling monomers.
Conventional biosensors include, for example, micro-cantilever biosensors, bioluminescent bioreporter sensors, fiber optic probe biosensors, porous silicon optical interferrometric biosensors, and biomimetic sensors. Micro-cantilever biosensors comprise a MEMS sensor chip operatively associated with an electronic readout chip. This type of biosensor has been used for biological sensing using antibody-antigen interaction. Additionally, such micro-cantilever biosensors have been used to measure concentrations of toluene, acetone, methanol and formaldehyde. The micro-cantilevers typically used in this type of biosensor comprise silicon or silicon nitride.
Bioluminescent bioreporter sensors comprise bioreporter organisms directly interfaced with an integrated circuit. The bioreporter organisms, which may be genetically engineered, luminesce when an analyte is detected and the IC detects the optical signal. Currently, various materials are being considered for entrapment of the cells at or near the light sensing portion of the IC, including agar/agarose, alginate, carrageenan, polyurethane, and ployacrylamide. Entrapment is essential for maintaining population viability, providing nutrients, interfacing with the IC, and providing protection from environmental conditions. Bioluminescent bioreporter integrated circuit sensors have been successfully employed to detect naphthalene, benzene, toluene, ethylbenzene, xylene polychlorinated biphenyl (PCB). Bioluminescent bioreporters have also been designed for detecting isopropylbenzene, monitoring heat shock gene expression, monitoring oxidative stress , detecting of mercury, and detecting alginate production in biofilms.
Fiber optic probe biosensor devices have been developed for remote detection of aerosolized bacteria. One such biosensor device comprises a fiber optic biosensor probe integrated with an automatic fluidics unit, a cyclone type air sampler, a radio receiver and batteries on a small remotely operated airplane. The biosensor is capable of running multiple simultaneous immuno assays in the evanescent wave region of the optical fiber. When the probe is in contact with a sample containing an analyte, an immobilized antibody specifically binds the analyte from the bulk solution. Any fluorophores are also bound in the evanescent region. Excitation of the fluorophore by light in the evanescent region (using a laser fluorimeter) leads to a detectable signal. Fiber optic probes have been used for analyzing clinical samples for pathogens, food samples for toxins, ground water samples for pollutants, and environmental samples for biological warfare agents. One remote biosensor uses a biotin-avidin system to link antibodies on the tapered distal end of the fiber optic probe. This system can easily be adapted for multi analyte sensing by changing the bound antibodies on the fiber optic probe. Use of avidin-biotin cross linking method increases the sensitivity and reduces non specific interactions by passivating the glass surface against non specific antibodies.
Porous silicon based optical interferrometric biosensors change color to signal the presence of various molecules. The basis of this technology is observing the change in the optical interference pattern. Chemical recognition molecules such as strands of DNA or antibodies are seeded on the surface of a porous silicon chip. The effective optical thickness of the medium can be correlated with the order and the wavelength of a peak in the spectral interferrogram. Consequently, the Fourier transform of the intensity-energy relationship can be used to calculate the effective optical thickness of the interference layers. The change of the effective optical thickness (product of refractive index and thickness) caused by the biological binding will shift the interference pattern to longer or shorter wavelength depending on the index-modifying mechanism involved, resulting in the emission of different colors and can be used as a very sensitive method for biosensing. The photoluminiscence of the porous silicon is due to the existence of nano/quantum sized silicon crystals. A portable hand held biosensor has been developed using this technology to detect a wide variety of compounds. This device can be used for detecting DNA, antibodies and biotin/avidin systems.
Biomimetic sensors do not use a biological element per se for detecting an analyte, but rather mimic a biological process using chemical reactions. Biomimetic sensors typically comprise a porous solid state substrate which is transmitive to light, such as, for example, a silica gel, a porous silicon dioxide and a porous, leached borosilicate glass; a light emitting diode and phototransistor for detecting the transmitted light; and a self regenerating chemical sensing agent impregnated into the substrate. In one such biomimetic sensor designed for detection of carbon monoxide, the chemical sensor agent is a supramolecular organometallic chemical complex, which mimics the function of hemoglobin, self assembled onto the surface of the solid substrate. The chemical sensing agents for CO detection are a mixture of soluble palladium salts, molybdenum and/or tungsten salts, copper salts, molecular encapsulants such as alpha cyclodextrin. Upon exposure of the solid state sensor to CO, the chemical reagent undergoes changes in its optical density. In CO free air, the chemical sensing elements can reverse their spectral shift by a self-regeneration process with a rate proportional to the rate of decrease of CO in the environment. The response characteristics (sensitivity and response time) of the sensor can be designed to meet specific standards or applications by controlling the formulation process of the chemical sensing agent. U.S. Pat. 5,063,164, discloses a biomimetic sensor developed for ethylene detection.
It is an object of the present invention to provide a biosensor for real time monitoring a selected aspect of an air conditioning or a refrigeration process and system.
In one disclosed embodiment, a biosensor is provided for detecting bacteria, fungi, metabolites, volatile organic compounds or specific allergens in a residential or commercial building air conditioning system.
In another disclosed embodiment, a biosensor is provided for detecting the presence of refrigerant leaking from the evaporator coils in a residential or commercial system. The detection of refrigerant leaks is of critical concern because of potential adverse atmospheric environmental effects and the toxicity characteristics of several alternative refrigerants.
In a further disclosed embodiment, a biosensor is provided for detecting the growth of bacteria or fungi in an air conditioning or a refrigeration system; such as, for example, detecting the presence of Legionella bacteria in a commercial building air conditioning system, water heater or cooling tower, or detecting the presence of Ecoli bacteria in a refrigerated food storage container.
In a still further disclosed embodiment, a biosensor is provided for detecting the presence and/or measuring the concentration of certain metabolites indicative of fruit or vegetable ripening or food spoilage, for example ethylene, in a refrigerated food storage container.
In a still further disclosed embodiment, a biosensor is provided for detecting the presence and/or measuring the concentration of carbon dioxide in a refrigerated transport container for perishable products being maintained in a reduced oxygen environment. Such a biosensor may also be used to monitor the concentration of carbon dioxide in a room so as to provide a control signal for use in controlling ventilation of fresh air into the room.
In a still further disclosed embodiment, a biosensor is provided for detecting the presence of a chemical that is a byproduct of corrosion of a metal component.
In a still further disclosed embodiment, a biosensor is provided for detecting the presence of hydrogen gas in absorption chiller, such as, for example, an absorption chiller of a commercial building air conditioning system. The hydrogen gas concentration within the chiller is indicative of the amount of corrosion within the chiller.